Spark plugs most likely. With an 04 model.....have fun, bless you, let me think of anything else to say for encouragement..... And change the coil boots while you're at it(probably swearing at it).

 

Ok, I'll try and check the plugs. But wouldn't this problem occur more than just at a certain rpm range? It happens right around 1100 or 1200.

 

Yea, I haven't gotten any codes, and I had a transmission guy check my truck and run his diagnostics but he couldn't duplicate the problem

I'm not really sure how many miles on the spark plugs since I bought it used, but I've put 30,XXX on it myself and I don't think the other owner would have changed them but I don't know. I haven't cleaned them recently but I cleaned them about 2 months ago

 

Yea I heard changing the spark plugs on these trucks is a nightmare. What so you mean coil boots?

 

Def plug or coil i had the exact same prob

 

My bad- I went back and saw you have the 4.6L engine. Good, you won't have a problem. But there is a little "boot" that goes from the coil pack to the plug, the equivalent to a plug wire. sometimes they get damaged when changing plugs, so best to get them while at-it with the plugs rather than go back.

 

It would be best and least expensive to start out with a plug change, maybe even go ahead and do the coil packs. To me, if you have to pull the plugs it's kind of crazy not to replace them unless you dont have the cash. The coils may be fine when cold but when the motor heats up they could be arcing from the coil or the boot to the motor. They breakdown over time and still fire but can be weak due to internal breakdown.

 

The original problem he stated was a shudder...not a studder...a shudder to me is a vibration...

 

When did your problem happen? Cause if it's a bad plug or coil I thought it would be all the time? Not just at a certain rpm range

 

My friend had an 04 XLT that had the exact same problem. I changed his COP and Spark plugs and it runs fine now.